Question

A female light brown (lilac) of genotype ww bb CC dd aa produced a litter of four kittens:   1 black kitten, 1 gray kitten, 1 brown tabby, 1 lilac (light brown) tabby

1. What were the genotype and the phenotype of the father?

2. Could these parents produce a lilac (same phenotype as the mother?) Show your work.

Answer 1

We have five loci w, b, c, d and a, and we have 5 kitten colors: black, gray, brown tabby, lilac tabby and lilac. The mother is recessive homologous for all the loci except C in which is dominant homozygous.

To answer this we need to first be clear on what each locus does to kitten color.

A. Agouti locus, this one gives the tabby pattern, a dominant A produces the tabby fur

B. Black locus, a dominant B gives black coloration.

C. The pointcolor locus, the recessive c shows the point coloration (like siamese cats), it needs to be cc to get expressed

D. The density locus, a dominant D allele gives an dark color, and the recessive gives a light coloration

W. White locus is dominant over all the other loci, the dominant W will produce a white fur, the recessive w will allow all the other loci to express

Now we can work to determine the kittens' and father genotypes. But first let's analyze the mother's gennotype:

ww bb CC dd aa

ww means she has no "white" alleles, bb means she has no "black" alleles (this means any black kitten is because of the father exclusively), CC means she has no pointcolor alleles, dd means she has light color alleles (any brown kitten is because of the father exclusively, but she is half responsible for every gray or lilac kitten), and aa means she has no "tabby" alleles (any tabby kitten is because of the father exclusively).

Now let's analyze the babies:

Black kitten: He has a dominat B so he's Bb (BB is not an option because the mother is bb), he's not tabby then he's aa, he's no pointcolor then he's CC, he's black so he's either Dd (DD is not an option since the mother is dd), and he's ww since he's not white. In order is: ww Bb CC Dd aa

Gray kitten: Gray coloration comes from Black B and light coloration d so he's Bb dd, he's not white nor colorpointed nor tabby so he's ww CC aa. In order that is: ww Bb CC dd aa

Brown tabby kitten: Brown color comes from recessive b and dark color D so he's bb Dd, tabby comes from dominant A so he's Aa, he's not white nor pointcolores so he's ww CC. In order that is: ww bb CC Dd Aa

Lilac tabby kitten: Lilac (lighr brown) comes from dd and bb, he tabby so that's Aa, he's not white nor pointcolored so ww CC. In order: ww bb CC dd Aa

Kittens are:

ww Bb CC Dd aa

ww Bb CC dd aa

ww bb CC Dd Aa

ww bb CC dd Aa

Now we can guess the father's genotype about each loci:

w: He might be either ww or Ww, but the second one has low probabilities (we would know that if we knew his phenotype)

b: He's Bb

c: He might be either CC or Cc, but the second one has low probabilities (we would know that if we knew his phenotype)

d: He's Dd

a: He's Aa

1.- What were the genotype and genotype of the father?

The genotype is either of this 4 options ww Bb CC Dd Aa, Ww Bb CC Dd Aa, ww Bb Cc Dd Aa, or Ww Bb Cc Dd Aa. But the most probable is ww Bb CC Dd Aa, and the phenotype related to that is a black tabby cat.

2.- Could these parents produce a lilac (same phenotype as the mother)?

Yes it is posible, these are the parents phenotype:

ww bb CC dd aa   ww Bb CC Dd Aa

And both have a recessive allele to done for each loci, and the dominant alleles for C locus to produce the same lilac phenotype.